Fireblocking device

ABSTRACT

Fireblocking device for preventing transfer of fire through ventilating apertures or similar passages, in openings for thermal fire ventilation, in ventilation ducts, in process plants or in vented facade exteriors, in vented fire blankets, vented fire protective curtains or vented protective screens against explosions. The device includes a combination of a heat absorbing and heat storing body, and an element which includes and/or adsorbs and intumescent material.

The invention relates to a fire blocking device as indicated in claim 1,in particular for blocking flames, which can be transferred throughventilation grates and similar apertures with air transfer. With“fireblocking device” is here ment a passive element, open for airtransfer, which prevents the spreading of fire by penetration of flames,heat conduction, convection or radiation.

BACKGROUND

Open flame arresters are known, which function as heat sink forexplosive combustion or short-lived fireballs. They are arranged open,so that air transfers, but not flames. They are often made of steel,either as perforated plates or mesh or as steel strip bodies pressedtogether, and similar. The function of arresting deflagration combustionfirst became known as Davy's net in 1815, used by Sir Humphrey Davy, andsuch elements have been used for different industrial purposes, such asfor engine block ventilation and in gas production facilities, asexplosion flame shields for personal safety offshore and similar.

Building fires are in some instances transferred by flames spreadingthrough openings and channels containing or being adjacent tocombustible elements or materials.

An example of such a risk in buildings are the inlets to ventilated,non-heated roofs (voids) or attics, where flames on the outside of awall or from a window, can spread through ventilators in eaves and intocombustible structures in attics. Such areas are not easy accessible,and fires that take hold here, often result in dramatic consequences.

Such fire spreading is hard to stop, and thus far one has not consideredit possible to combine the demand for venting and fire resistance.Activateable dampers are considered to be too unsafe because flames canpass for minutes before closing, because of the weathering, because ofmechanical and movable parts and because of dry materials, which canignite before closing.

From U.S. Pat. No. 5,565,274 (Perrone et al.) it is known for instancean attic hatch, which comprises intumescent material and which is closedwith a heat-triggered activator.

From U.S. Pat. No. 5,811,731 (Jacques et al.) it is known to line anintumescent material around a cable channel. There are vents forconducting excess heat from cables and a steel grille, which will bedisintegrated in case of a fire.

Known patents and solutions for preventing fire spreading in openingsfor air passages have a weakness in that, during a period before theyare activated, they allow flames to pass through and ignite combustiblegas or easily ignitable solid materials on the side that shall beprotected. Some of them also leave cracks, which make flame tongues andsmoke spreading possible, even when they are closed.

OBJECT

The main object of the invention is to create a passive fireblockingdevice for air passages, which instantly, i.e. from the firstmillisecond and until the openings are shut, can prevent fire fromspreading via the air passage from one area with a fire, to a room, ductor other building or machine voids, where fire can cause damage and/orspread further to other and vulnerable areas with combustible materialsthat can spread a fire.

In particular, it is an object to create an element, which can be builtinto vents in buildings, such as in eaves, where air passage isrequired, to prevent fire from spreading through such passages or otherpassages, which must not spread fire.

It is also a particular object to prevent ignition of combustible gas orcombustible solid material on the protected side from the very firstimpact of heat, conducted heat or deflagration burning from the outside,and through the entire period, the element is designed to perform.

THE INVENTION

The invention is indicated in claim 1. With “grille body” is meant anybody that allows flow through a plurality of evenly distributedopenings, where each opening is small compared to the totalcross-section of the body.

Examples of applications of the invention are as vents in walls,bulkheads, tanks, ducts, openings for natural ventilation, in processingplants, vented facade exteriors, vented fire blankets, open fireprotective curtains or open protective screen against explosions.

When used for instance in vented roofs or vulnerable eaves, thefireblocking devices according to the invention will prevent flamespreading whithout blocking air passage. At the same time, birds,insects, leaves and sparks are kept out. The air velocity may be reducedin regard to previous venting gaps between soffit boards, but this maybe an advantage, as new research indicates that former regulations wereexaggerated and thus not very energy saving.

The fireblocking devices according to the invention can be produced atlow cost with cheap materials. Installation of the fireblocking deviceor post-installation with replacement of existing ventilating grilles,respectively, can take place without any particular training and in aneasy manner. Furthermore, it is possible to make the fireblocking deviceaccording to the invention maintenance-free and nearly everlasting.

Additional advantageous features of the invention are indicated inclaims 2-8. These will be described further in connection with anexample of embodiment, which discloses further details of the invention.

EXAMPLE

The invention will be further described below with reference to thedrawings, where

FIG. 1 illustrates a schematic perspective view of an embodiment of theinvention, and

FIG. 2 correspondingly illustrates a schematic cross-section through theelement in FIG. 1, in a possible application.

FIG. 1 shows a fireblocking device 11 according to the invention, whichis made up of a lower, rectangular plate 12 of a grille that is treatedwith an intumescent material, and an upper corresponding rectangularplate 13 of a heat absorbing and heat storing material 14, through whichair can flow. Over this, there is placed a rim frame 15 of aheat-insulating material, which can interrupt a heat bridge. Such aheat-insulating frame can alternatively or additionally be placedbetween the two plates 12 and 13.

This embodiment requires an upwardly directed flame in the direction 16from below, as will be apparent from the following.

The two elements can have an arbitrary shape, depending on the field ofapplication. They can also be made as plate material intended fordivision into pieces at the location of use. The arrangement of the twoparts of the fireblocking device as indicated above, gives particularadvantages because the intumescent material will be exposed to flameswith maximum temperature. But it is also possible that the basic effectof the invention can be achieved in that the heat absorbing and heatstoring element first and the tightening element lies behind this, inthe direction of the flow.

It may also be possible to combine the two elements so that the heatsink effect and the tightening effect is obtained totally or partiallyby the same element.

The lower grille plate 12 is manufactured in a generally known manner asa perforated body of, or coated with, or treated with an intumescentmaterial 17, i.e. a material that swells and tightens all openings whenheated. This material may cover for instance 10-20% of the flow-througharea. The intumescent material can be based on high density polyethylenin hard phase of thermoplastic elastomer and chlorinated polyethylenand/or silicone rubber in soft phase. The material contains typicalbinding agent, thermal stabilizing material, fire retardant additive,and crust forming additives.

The lower grille plate 12 can also be manufactured as a metal grillewith an intumescent material embedded in pockets or voids.

The upper mesh 13 can be one or more perforated plates, ahoneycomb-shaped grid of steel plate, pipe metal filled with liquid, abody mainly comprised of coiled or pressed together metal threads orbands, possibly combined with small stones, steel pellets or heatconduction contact with another material that has sufficient thermalconductivity and heat storage capacity.

A fireblocking device according to the invention can be used in variousapplications. It is suitable for buildings, especially in connectionwith vented attics and as ventilating grilles for ducts and voids thatcontains combustible material, or which can transfer flames to othercombustible structures. Additional fireblocking devices according to theinvention can be arranged after one another in a duct or in a transitionarea.

Examples of applications of the invention are vents in walls, bulkheads,tanks, ducts, openings for natural ventilation, in processing plants,vented facade exteriors, vented fire blankets, open fire protectivecurtains or open protective screens against explosions.

Fire blanket involves a fabric/tarpaulin/curtain in the form of anetting, where a part of the netting is heat absorbing and another partis intumescent. It can be used to extinguish car and house fires and toprotect persons against fire. In this way, the blanket is light, andwhen it is pulled over a burning object, pressure does notincrease—something which otherwise makes it impossible to use tight fireblankets—and fire does not slip through. When it becomes tight by theintumescent part and thus is affected by heat impetus, one has had thetime to get it well secured in place and fastened, and the fire issmothered by its own smoke.

The safety curtains resemble fire blankets and is usually transparent,but protect persons against heat radiation from explosions or fires inthe industry, in fire experiments, in laboratories or in firedemonstrations in auditoriums. Safety curtains can be used where sound,visibility, smell or pressure balancing—or all—is required,simultaneously with fire protection for persons or values.

Known techniques for protecting persons against explosions by combustionare very heavy constructions of concrete, or guiding the combustionfront and the pressure wave into the open or into large volumes of airthat perform as a buffer. The first technique may fail in powerfulexplosions, as well as being expensive and inconvenient. The latter doesnot provide protection against heat radiation and flaming combustion,only against the pressure impact. The present invention as a protectivescreen involves pressure-reducing air passages, pressure-reducingmovable curtains, no passage of heat radiation and a totally gas-tightpatition if the explosion is succeeded by fire. The protective screenagainst explosion resembles a safet y curtain, but has the necessarymechanical design to withstand an explosion.

The advantages of a fireblocking device according to the invention canbe summarized as follows:

-   -   No mechanical movable parts    -   It can be installed into fire barriers, protective hoods, pipes,        ducts, vented dressings, vented roofs and attics    -   It prevents fire spreading by heat convection, instantaneously        and during the entire fire resistance period    -   It prevents fire spreading by heat radiation, instantaneously        and during the entire fire resistance period    -   It prevents fire spreading by heat conduction, instantaneously        and during the entire fire resistance period    -   It is non-combustible    -   It prevents fire spreading by explosion combustion, diffuse        flame combstion and fire ball    -   It becomes gas tight from impact of heat from fire    -   It can be cleaned by flushing    -   It can be post-installed into existing constructions

FIG. 2 shows an example of a possible field of application, where afireblocking device 12, as shown in FIG. 1, is built into theventilating aperture 18 in a soffit at eaves 19 under a roof 20.

1. Fireblocking device (11) for continuously preventing in a flameimpact period the transfer of flames through ventilating apertures orsimilar passages, in openings for thermal fire ventilation, inventilation ducts, in process plants or in vented facade exteriors,characterized by at least one permeable flame blocking and heatabsorbing and heat accumulating grille body (13) to stop flames duringinstant and constant flame impact in the initial phase of flame impact,and at least one permeable element (12) containing and/or incorporatingan intumescent material, for permanent fire stopping in the last phaseof the flame impact period.
 2. Fireblocking device according to claim 1,characterized in that the heat absorbing and heat storing body (13) isthree-dimensional.
 3. Fireblocking device according to claim 2,characterized in that it is shaped as a cylinder.
 4. Fireblocking deviceaccording to claim 3, characterized in that the heat absorbing and heatstoring body (13) can contain metal pipes filled with liquid, mineralsor mixes of these materials as main element.
 5. Fireblocking deviceaccording to claim 4, characterized in that the heat absorbing and heatstoring body (13) comprises honeycomb-patterned sheet-metal, which canbe arranged into a frame, which includes a thermal break. 6.Fireblocking device according to claim 1, characterized in that the heatadsorbing perforated body (13) is positioned downstream of the semi-openelement (12), and which contains intumescent material, positionedtowards the flame front.
 7. Fireblocking device according to claim 1,characterized in that it is provided as sheet material.
 8. (canceled)